View Javadoc

1   /*
2    * Licensed to the Apache Software Foundation (ASF) under one
3    * or more contributor license agreements.  See the NOTICE file
4    * distributed with this work for additional information
5    * regarding copyright ownership.  The ASF licenses this file
6    * to you under the Apache License, Version 2.0 (the
7    * "License"); you may not use this file except in compliance
8    * with the License.  You may obtain a copy of the License at
9    *
10   *   http://www.apache.org/licenses/LICENSE-2.0
11   *
12   * Unless required by applicable law or agreed to in writing,
13   * software distributed under the License is distributed on an
14   * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
15   * KIND, either express or implied.  See the License for the
16   * specific language governing permissions and limitations
17   * under the License.
18   */
19  
20  package org.apache.myfaces.orchestra.viewController;
21  
22  /**
23   * An interface for use with the InterfaceViewControllerExecutor.
24   * <p>
25   * When the InterfaceViewControllerExecutor has been selected as the technique for mapping
26   * lifecycle events onto bean methods, then the target bean must implement this interface
27   * in order to get callbacks.
28   * <p>
29   * Note that the expression "view controller bean" is used to generally refer to an object
30   * that can handle lifecycle events for a view. Such beans may implement this interface, but
31   * may not - they might be accessed via the ReflectiveViewControllerExecutor or other
32   * implementations that do not require this interface. 
33   */
34  public interface ViewController
35  {
36      /**
37       * This method will <i>always</i> be called before any other method is invoked
38       * on any backing bean for the current request. It is invoked once for each
39       * request.
40       * <p>
41       * This callback could possibly be better named "notifyBeginRequestUsingThisView"
42       * or similar, as it is invoked per request.
43       * <p>
44       * There are three different situations in which initView callbacks occur:
45       * <ol>
46       * <li>
47       * A view is just being rendered.<br>
48       * The initView callback gets called once (at BeforeRender)
49       * </li>
50       * <li>
51       * A postback is processed, no navigation occurs.<br>
52       * The initView callback gets called once (at AfterRestoreView)
53       * </li>
54       * <li>
55       * A postback occurs, navigation to a different view instance occurs.<br>
56       * The initView callback gets called once for the original view, and then once for the new view.
57       * </li>
58       * </ol>
59       * <p>
60       * Note that the condition tested is whether the <i>view instance</i> has changed; if navigation causes
61       * a new view root to be created then the initView callback occurs even if that view root has the
62       * same viewId [1].
63       * <p>
64       * Note [1]: Orchestra versions 1.3 and earlier test only the viewId string.
65       */
66      public void initView();
67  
68      /**
69       * This method will be invoked before any "action" callbacks related to buttons,
70       * links, etc. are invoked on backing beans for the current request.
71       * <p>
72       * For JSF, there is an exception: for command components marked as "immediate",
73       * the associated action method is invoked before this callback occurs. If that
74       * method then performs navigation then this callback will not occur at all.
75       * <p>
76       * Note also that for JSF, if validation failures occur then this callback will
77       * not be invoked (as actions are skipped).  
78       */
79      public void preProcess();
80      
81      /**
82       * This method will be invoked just before starting to render output to the user.
83       */
84      public void preRenderView();
85  }